Heretofore, a solenoid valve system has been known in which plural solenoid valve units are connected to make up a manifold, the system further comprising a safety apparatus or a safety countermeasure for the purpose of avoiding abnormalities or malfunctioning of solenoid valves in each of the solenoid valve units.
In such a solenoid valve system, for example, in a serial transmission unit that outputs control signals to the solenoid valve units, or in a circuit that outputs control signals to adjacent solenoid valve units among a plurality of solenoid valve units, malfunctioning due to failures or the like is known to occur. In this case, as a safety apparatus or a safety countermeasure, it is necessary for a condition to occur in which a solenoid valve unit cannot be controlled, even though a control signal is input to a solenoid valve of the solenoid valve unit exhibiting such an abnormality.
Thus, as disclosed in Japanese Laid-Open Patent Publication No. 2003-139264, the present applicant has proposed a solenoid valve control apparatus equipped with an interlock unit located between a serial transmission unit, which outputs control signals respectively to a plurality of solenoid valve units, and which carries out an interlock control with respect to all of the solenoid valve units. In this case, as a result of the interlock unit subjecting common signals, which are output to the solenoid valve units from the serial transmission unit, to such an interlock control, the interlock control is performed comprehensively with respect to the solenoid valve control apparatus as a whole.
Further, in the specification of European Patent No. EP 2026156 B1, a safety module is disclosed having a switching means for a power source supply line, such that, in a condition in which the switching means is actuated, a valve module power source supply line, by which power is supplied via the safety module, is interrupted.